Sensory integration

This garden universe vibrates complete. Some we get a sound so sweet. Vibrations reach on up to become light, and then thru gamma, out of sight. Between the eyes and ears there lay, the sounds of color and the light of a sigh. ~ Moody Blues

A recent study shows that baboons can learn to tell the difference between word and non-word strings [ link ]. In an accompanying editorial, Dr Michael Platt says this evidence suggests dyslexia might be more of a visual problem than a problem matching sounds to letters. It’s a rare opportunity that I get to hear a neuroscientist jump to an either-or conclusion like that. Reading is an integrated process that coops many areas of the brain. A problem in the visual system can produce a reading deficit just as profound as a problem in the auditory system. These systems are integrated by higher centers of the brain during reading. What these investigators discovered with baboons is a better example of pattern recognition. It’s a process shared by any species that survives in the wild. Over time, the visual system is tuned to distinguish what’s meaningful from what isn’t by a process of ‘statistical regularity’. Statistical regularity simply means that certain signal combinations appear more frequently with meaningful objects than with non-meaningful objects. It’s no surprise that a baboon can perform this with a string of letters just as easily as it can a set of racing stripes. And I have no doubt that humans require a working visual system as well as a sound system to be able to read coherently. The written word hasn’t been around long enough to evolve an area of it’s own in the brain like it has for speech and vision.